1. Field of the Invention
The present invention relates to a method for manufacturing a nitride layer and a method for fabricating a vertical nitride semiconductor light emitting device using the same. More particularly, the present invention relates to a method for manufacturing a nitride layer which releases heat generated in the decomposition of the nitride layer through a buffer layer and prevents heat-induced deterioration of the nitride layer by adjusting an intensity of a laser beam irradiated in a laser lift off (LLO) process after growth of the nitride layer on a sapphire substrate to remove the nitride layer at an interface between the nitride layer and a buffer layer, and a method for fabricating a vertical nitride semiconductor device using the same.
2. Description of the Related Art
Due to recent drastic developments in telecommunication technologies, communication techniques for high-speed and massive-capacity signal transmission have experienced a rapid development. Especially, with a rising demand for personal mobile phones, satellite communications, military radars, broadcasting communications and communication relays, there has been an increasing request for a high-speed, high-power electronic device which requires a high-speed telecommunication system of microwave band and millimeter wave band. In particular, a nitrogen compound (nitride) has a large energy gap, and exhibits superior physical properties such as a high thermal chemical stability and a high electronic saturation velocity. Therefore the nitride is easily applicable not only to an optical device but also to a high-frequency, high-power electronic device, and thus has been actively studied in wide-ranging areas.
In a conventional method to obtain such nitride semiconductor, a sapphire substrate was used to grow a nitride layer thereon. But the sapphire substrate is an insulating material with poor thermal conductivity that can be hardly processed. This disadvantageously complicates a manufacturing process of the device and hinders improvement in capacities thereof. To overcome such problems, the sapphire substrate was removed from the nitride layer via a laser lift off (LLO) process.
FIG. 1 is a sectional view illustrating a method for fabricating a nitride layer via a conventional LLO process. Referring to FIG. 1, in the conventional method to fabricate the nitride layer, first, a buffer layer 11 made of AlN or GaN is formed on a sapphire substrate 10. Then, a nitride layer 12 is grown on the buffer layer 11. Thereafter, a laser beam L is irradiated to an underside of the sapphire substrate 10. The irradiated laser beam transmits the sapphire substrate 10 and decomposes the buffer layer 11, thus enabling separation of the nitride layer 12. That is, in the conventional method to fabricate the nitride layer, the buffer layer 11 serves as a sacrificial layer to separate the nitride layer 12 from the sapphire substrate 10.
In this fashion, due to the buffer layer 11 used as a sacrificial layer in the conventional nitride layer manufacturing method, about 1000° C. heat is transferred to the nitride layer 12, thus deteriorating the nitride layer 12. This disadvantageously degrades physical properties of the nitride layer and also optical and electrical properties.